Merge branch 'tcp-rbtree-retransmit-queue'

Eric Dumazet says:

====================
tcp: implement rb-tree based retransmit queue

This patch series implement RB-tree based retransmit queue for TCP,
to better match modern BDP.

Tested:

 On receiver :
 netem on ingress : delay 150ms 200us loss 1
 GRO disabled to force stress and SACK storms.

for f in `seq 1 10`
do
 ./netperf -H lpaa6 -l30 -- -K bbr -o THROUGHPUT|tail -1
done | awk '{print $0} {sum += $0} END {printf "%7u\n",sum}'

Before patch :

323.87  351.48  339.59  338.62  306.72
204.07  304.93  291.88  202.47  176.88
->   2840

After patch:

1700.83 2207.98 2070.17 1544.26 2114.76
2124.89 1693.14 1080.91 2216.82 1299.94
->  18053

Average of 1805 Mbits istead of 284 Mbits.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -3158,6 +3158,12 @@ static inline int __skb_grow_rcsum(struct sk_buff *skb, unsigned int len)
 	return __skb_grow(skb, len);
 }
 
+#define rb_to_skb(rb) rb_entry_safe(rb, struct sk_buff, rbnode)
+#define skb_rb_first(root) rb_to_skb(rb_first(root))
+#define skb_rb_last(root)  rb_to_skb(rb_last(root))
+#define skb_rb_next(skb)   rb_to_skb(rb_next(&(skb)->rbnode))
+#define skb_rb_prev(skb)   rb_to_skb(rb_prev(&(skb)->rbnode))
+
 #define skb_queue_walk(queue, skb) \
 		for (skb = (queue)->next;					\
 		     skb != (struct sk_buff *)(queue);				\
@@ -3172,6 +3178,18 @@ static inline int __skb_grow_rcsum(struct sk_buff *skb, unsigned int len)
 		for (; skb != (struct sk_buff *)(queue);			\
 		     skb = skb->next)
 
+#define skb_rbtree_walk(skb, root)						\
+		for (skb = skb_rb_first(root); skb != NULL;			\
+		     skb = skb_rb_next(skb))
+
+#define skb_rbtree_walk_from(skb)						\
+		for (; skb != NULL;						\
+		     skb = skb_rb_next(skb))
+
+#define skb_rbtree_walk_from_safe(skb, tmp)					\
+		for (; tmp = skb ? skb_rb_next(skb) : NULL, (skb != NULL);	\
+		     skb = tmp)
+
 #define skb_queue_walk_from_safe(queue, skb, tmp)				\
 		for (tmp = skb->next;						\
 		     skb != (struct sk_buff *)(queue);				\

include/net/sock.h

@@ -60,7 +60,7 @@
 #include <linux/sched.h>
 #include <linux/wait.h>
 #include <linux/cgroup-defs.h>
-
+#include <linux/rbtree.h>
 #include <linux/filter.h>
 #include <linux/rculist_nulls.h>
 #include <linux/poll.h>
@@ -397,7 +397,10 @@ struct sock {
 	int			sk_wmem_queued;
 	refcount_t		sk_wmem_alloc;
 	unsigned long		sk_tsq_flags;
-	struct sk_buff		*sk_send_head;
+	union {
+		struct sk_buff	*sk_send_head;
+		struct rb_root	tcp_rtx_queue;
+	};
 	struct sk_buff_head	sk_write_queue;
 	__s32			sk_peek_off;
 	int			sk_write_pending;

include/net/tcp.h

@@ -551,7 +551,13 @@ void tcp_xmit_retransmit_queue(struct sock *);
 void tcp_simple_retransmit(struct sock *);
 void tcp_enter_recovery(struct sock *sk, bool ece_ack);
 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
-int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
+enum tcp_queue {
+	TCP_FRAG_IN_WRITE_QUEUE,
+	TCP_FRAG_IN_RTX_QUEUE,
+};
+int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+		 struct sk_buff *skb, u32 len,
+		 unsigned int mss_now, gfp_t gfp);
 
 void tcp_send_probe0(struct sock *);
 void tcp_send_partial(struct sock *);
@@ -1606,19 +1612,11 @@ static inline void tcp_skb_tsorted_anchor_cleanup(struct sk_buff *skb)
 	skb->_skb_refdst = _save;		\
 }
 
-/* write queue abstraction */
-static inline void tcp_write_queue_purge(struct sock *sk)
-{
-	struct sk_buff *skb;
+void tcp_write_queue_purge(struct sock *sk);
 
-	tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
-	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
-		tcp_skb_tsorted_anchor_cleanup(skb);
-		sk_wmem_free_skb(sk, skb);
-	}
-	INIT_LIST_HEAD(&tcp_sk(sk)->tsorted_sent_queue);
-	sk_mem_reclaim(sk);
-	tcp_clear_all_retrans_hints(tcp_sk(sk));
+static inline struct sk_buff *tcp_rtx_queue_head(const struct sock *sk)
+{
+	return skb_rb_first(&sk->tcp_rtx_queue);
 }
 
 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
@@ -1643,18 +1641,12 @@ static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
 	return skb_queue_prev(&sk->sk_write_queue, skb);
 }
 
-#define tcp_for_write_queue(skb, sk)					\
-	skb_queue_walk(&(sk)->sk_write_queue, skb)
-
-#define tcp_for_write_queue_from(skb, sk)				\
-	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
-
 #define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
 	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
 
 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
 {
-	return sk->sk_send_head;
+	return skb_peek(&sk->sk_write_queue);
 }
 
 static inline bool tcp_skb_is_last(const struct sock *sk,
@@ -1663,29 +1655,30 @@ static inline bool tcp_skb_is_last(const struct sock *sk,
 	return skb_queue_is_last(&sk->sk_write_queue, skb);
 }
 
-static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
+static inline bool tcp_write_queue_empty(const struct sock *sk)
 {
-	if (tcp_skb_is_last(sk, skb))
-		sk->sk_send_head = NULL;
-	else
-		sk->sk_send_head = tcp_write_queue_next(sk, skb);
+	return skb_queue_empty(&sk->sk_write_queue);
+}
+
+static inline bool tcp_rtx_queue_empty(const struct sock *sk)
+{
+	return RB_EMPTY_ROOT(&sk->tcp_rtx_queue);
+}
+
+static inline bool tcp_rtx_and_write_queues_empty(const struct sock *sk)
+{
+	return tcp_rtx_queue_empty(sk) && tcp_write_queue_empty(sk);
 }
 
 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
 {
-	if (sk->sk_send_head == skb_unlinked) {
-		sk->sk_send_head = NULL;
+	if (tcp_write_queue_empty(sk))
 		tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
-	}
+
 	if (tcp_sk(sk)->highest_sack == skb_unlinked)
 		tcp_sk(sk)->highest_sack = NULL;
 }
 
-static inline void tcp_init_send_head(struct sock *sk)
-{
-	sk->sk_send_head = NULL;
-}
-
 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
 {
 	__skb_queue_tail(&sk->sk_write_queue, skb);
@@ -1696,8 +1689,7 @@ static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb
 	__tcp_add_write_queue_tail(sk, skb);
 
 	/* Queue it, remembering where we must start sending. */
-	if (sk->sk_send_head == NULL) {
-		sk->sk_send_head = skb;
+	if (sk->sk_write_queue.next == skb) {
 		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
 
 		if (tcp_sk(sk)->highest_sack == NULL)
@@ -1710,35 +1702,32 @@ static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *s
 	__skb_queue_head(&sk->sk_write_queue, skb);
 }
 
-/* Insert buff after skb on the write queue of sk.  */
-static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
-						struct sk_buff *buff,
-						struct sock *sk)
-{
-	__skb_queue_after(&sk->sk_write_queue, skb, buff);
-}
-
 /* Insert new before skb on the write queue of sk.  */
 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
 						  struct sk_buff *skb,
 						  struct sock *sk)
 {
 	__skb_queue_before(&sk->sk_write_queue, skb, new);
-
-	if (sk->sk_send_head == skb)
-		sk->sk_send_head = new;
 }
 
 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
 {
-	list_del(&skb->tcp_tsorted_anchor);
-	tcp_skb_tsorted_anchor_cleanup(skb);
 	__skb_unlink(skb, &sk->sk_write_queue);
 }
 
-static inline bool tcp_write_queue_empty(struct sock *sk)
+void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb);
+
+static inline void tcp_rtx_queue_unlink(struct sk_buff *skb, struct sock *sk)
 {
-	return skb_queue_empty(&sk->sk_write_queue);
+	tcp_skb_tsorted_anchor_cleanup(skb);
+	rb_erase(&skb->rbnode, &sk->tcp_rtx_queue);
+}
+
+static inline void tcp_rtx_queue_unlink_and_free(struct sk_buff *skb, struct sock *sk)
+{
+	list_del(&skb->tcp_tsorted_anchor);
+	tcp_rtx_queue_unlink(skb, sk);
+	sk_wmem_free_skb(sk, skb);
 }
 
 static inline void tcp_push_pending_frames(struct sock *sk)
@@ -1767,8 +1756,9 @@ static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
 
 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
 {
-	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
-						tcp_write_queue_next(sk, skb);
+	struct sk_buff *next = skb_rb_next(skb);
+
+	tcp_sk(sk)->highest_sack = next ?: tcp_send_head(sk);
 }
 
 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
@@ -1778,7 +1768,9 @@ static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
 
 static inline void tcp_highest_sack_reset(struct sock *sk)
 {
-	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
+	struct sk_buff *skb = tcp_rtx_queue_head(sk);
+
+	tcp_sk(sk)->highest_sack = skb ?: tcp_send_head(sk);
 }
 
 /* Called when old skb is about to be deleted (to be combined with new skb) */
@@ -1948,7 +1940,7 @@ extern void tcp_rack_reo_timeout(struct sock *sk);
 /* At how many usecs into the future should the RTO fire? */
 static inline s64 tcp_rto_delta_us(const struct sock *sk)
 {
-	const struct sk_buff *skb = tcp_write_queue_head(sk);
+	const struct sk_buff *skb = tcp_rtx_queue_head(sk);
 	u32 rto = inet_csk(sk)->icsk_rto;
 	u64 rto_time_stamp_us = skb->skb_mstamp + jiffies_to_usecs(rto);
 

net/ipv4/tcp.c

@@ -413,6 +413,7 @@ void tcp_init_sock(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 
 	tp->out_of_order_queue = RB_ROOT;
+	sk->tcp_rtx_queue = RB_ROOT;
 	tcp_init_xmit_timers(sk);
 	INIT_LIST_HEAD(&tp->tsq_node);
 	INIT_LIST_HEAD(&tp->tsorted_sent_queue);
@@ -469,8 +470,10 @@ void tcp_init_transfer(struct sock *sk, int bpf_op)
 	tcp_init_buffer_space(sk);
 }
 
-static void tcp_tx_timestamp(struct sock *sk, u16 tsflags, struct sk_buff *skb)
+static void tcp_tx_timestamp(struct sock *sk, u16 tsflags)
 {
+	struct sk_buff *skb = tcp_write_queue_tail(sk);
+
 	if (tsflags && skb) {
 		struct skb_shared_info *shinfo = skb_shinfo(skb);
 		struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
@@ -699,10 +702,9 @@ static void tcp_push(struct sock *sk, int flags, int mss_now,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
 
-	if (!tcp_send_head(sk))
-		return;
-
 	skb = tcp_write_queue_tail(sk);
+	if (!skb)
+		return;
 	if (!(flags & MSG_MORE) || forced_push(tp))
 		tcp_mark_push(tp, skb);
 
@@ -962,14 +964,14 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
 		int copy, i;
 		bool can_coalesce;
 
-		if (!tcp_send_head(sk) || (copy = size_goal - skb->len) <= 0 ||
+		if (!skb || (copy = size_goal - skb->len) <= 0 ||
 		    !tcp_skb_can_collapse_to(skb)) {
 new_segment:
 			if (!sk_stream_memory_free(sk))
 				goto wait_for_sndbuf;
 
 			skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation,
-						  skb_queue_empty(&sk->sk_write_queue));
+					tcp_rtx_and_write_queues_empty(sk));
 			if (!skb)
 				goto wait_for_memory;
 
@@ -1041,7 +1043,7 @@ wait_for_memory:
 
 out:
 	if (copied) {
-		tcp_tx_timestamp(sk, sk->sk_tsflags, tcp_write_queue_tail(sk));
+		tcp_tx_timestamp(sk, sk->sk_tsflags);
 		if (!(flags & MSG_SENDPAGE_NOTLAST))
 			tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
 	}
@@ -1197,7 +1199,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 			goto out_err;
 		}
 
-		skb = tcp_send_head(sk) ? tcp_write_queue_tail(sk) : NULL;
+		skb = tcp_write_queue_tail(sk);
 		uarg = sock_zerocopy_realloc(sk, size, skb_zcopy(skb));
 		if (!uarg) {
 			err = -ENOBUFS;
@@ -1273,7 +1275,7 @@ restart:
 		int max = size_goal;
 
 		skb = tcp_write_queue_tail(sk);
-		if (tcp_send_head(sk)) {
+		if (skb) {
 			if (skb->ip_summed == CHECKSUM_NONE)
 				max = mss_now;
 			copy = max - skb->len;
@@ -1293,7 +1295,7 @@ new_segment:
 				process_backlog = false;
 				goto restart;
 			}
-			first_skb = skb_queue_empty(&sk->sk_write_queue);
+			first_skb = tcp_rtx_and_write_queues_empty(sk);
 			skb = sk_stream_alloc_skb(sk,
 						  select_size(sk, sg, first_skb),
 						  sk->sk_allocation,
@@ -1418,7 +1420,7 @@ wait_for_memory:
 
 out:
 	if (copied) {
-		tcp_tx_timestamp(sk, sockc.tsflags, tcp_write_queue_tail(sk));
+		tcp_tx_timestamp(sk, sockc.tsflags);
 		tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
 	}
 out_nopush:
@@ -1519,6 +1521,13 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
 
 	/* XXX -- need to support SO_PEEK_OFF */
 
+	skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
+		err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
+		if (err)
+			return err;
+		copied += skb->len;
+	}
+
 	skb_queue_walk(&sk->sk_write_queue, skb) {
 		err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
 		if (err)
@@ -2318,6 +2327,37 @@ static inline bool tcp_need_reset(int state)
 		TCPF_FIN_WAIT2 | TCPF_SYN_RECV);
 }
 
+static void tcp_rtx_queue_purge(struct sock *sk)
+{
+	struct rb_node *p = rb_first(&sk->tcp_rtx_queue);
+
+	while (p) {
+		struct sk_buff *skb = rb_to_skb(p);
+
+		p = rb_next(p);
+		/* Since we are deleting whole queue, no need to
+		 * list_del(&skb->tcp_tsorted_anchor)
+		 */
+		tcp_rtx_queue_unlink(skb, sk);
+		sk_wmem_free_skb(sk, skb);
+	}
+}
+
+void tcp_write_queue_purge(struct sock *sk)
+{
+	struct sk_buff *skb;
+
+	tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
+	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) {
+		tcp_skb_tsorted_anchor_cleanup(skb);
+		sk_wmem_free_skb(sk, skb);
+	}
+	tcp_rtx_queue_purge(sk);
+	INIT_LIST_HEAD(&tcp_sk(sk)->tsorted_sent_queue);
+	sk_mem_reclaim(sk);
+	tcp_clear_all_retrans_hints(tcp_sk(sk));
+}
+
 int tcp_disconnect(struct sock *sk, int flags)
 {
 	struct inet_sock *inet = inet_sk(sk);
@@ -2376,7 +2416,6 @@ int tcp_disconnect(struct sock *sk, int flags)
 	 * issue in __tcp_select_window()
 	 */
 	icsk->icsk_ack.rcv_mss = TCP_MIN_MSS;
-	tcp_init_send_head(sk);
 	memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
 	__sk_dst_reset(sk);
 	dst_release(sk->sk_rx_dst);

net/ipv4/tcp_fastopen.c

@@ -465,17 +465,15 @@ bool tcp_fastopen_active_should_disable(struct sock *sk)
 void tcp_fastopen_active_disable_ofo_check(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct rb_node *p;
-	struct sk_buff *skb;
 	struct dst_entry *dst;
+	struct sk_buff *skb;
 
 	if (!tp->syn_fastopen)
 		return;
 
 	if (!tp->data_segs_in) {
-		p = rb_first(&tp->out_of_order_queue);
-		if (p && !rb_next(p)) {
-			skb = rb_entry(p, struct sk_buff, rbnode);
+		skb = skb_rb_first(&tp->out_of_order_queue);
+		if (skb && !skb_rb_next(skb)) {
 			if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
 				tcp_fastopen_active_disable(sk);
 				return;

net/ipv4/tcp_input.c

@@ -1142,6 +1142,7 @@ struct tcp_sacktag_state {
 	u64	last_sackt;
 	struct rate_sample *rate;
 	int	flag;
+	unsigned int mss_now;
 };
 
 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
@@ -1191,7 +1192,8 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 		if (pkt_len >= skb->len && !in_sack)
 			return 0;
 
-		err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC);
+		err = tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
+				   pkt_len, mss, GFP_ATOMIC);
 		if (err < 0)
 			return err;
 	}
@@ -1288,13 +1290,13 @@ static u8 tcp_sacktag_one(struct sock *sk,
 /* Shift newly-SACKed bytes from this skb to the immediately previous
  * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
  */
-static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
+static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
+			    struct sk_buff *skb,
 			    struct tcp_sacktag_state *state,
 			    unsigned int pcount, int shifted, int mss,
 			    bool dup_sack)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct sk_buff *prev = tcp_write_queue_prev(sk, skb);
 	u32 start_seq = TCP_SKB_CB(skb)->seq;	/* start of newly-SACKed */
 	u32 end_seq = start_seq + shifted;	/* end of newly-SACKed */
 
@@ -1363,8 +1365,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 	if (unlikely(TCP_SKB_CB(prev)->tx.delivered_mstamp))
 		TCP_SKB_CB(prev)->tx.delivered_mstamp = 0;
 
-	tcp_unlink_write_queue(skb, sk);
-	sk_wmem_free_skb(sk, skb);
+	tcp_rtx_queue_unlink_and_free(skb, sk);
 
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_SACKMERGED);
 
@@ -1414,9 +1415,9 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 		goto fallback;
 
 	/* Can only happen with delayed DSACK + discard craziness */
-	if (unlikely(skb == tcp_write_queue_head(sk)))
+	prev = skb_rb_prev(skb);
+	if (!prev)
 		goto fallback;
-	prev = tcp_write_queue_prev(sk, skb);
 
 	if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED)
 		goto fallback;
@@ -1495,18 +1496,17 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 
 	if (!skb_shift(prev, skb, len))
 		goto fallback;
-	if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
+	if (!tcp_shifted_skb(sk, prev, skb, state, pcount, len, mss, dup_sack))
 		goto out;
 
 	/* Hole filled allows collapsing with the next as well, this is very
 	 * useful when hole on every nth skb pattern happens
 	 */
-	if (prev == tcp_write_queue_tail(sk))
+	skb = skb_rb_next(prev);
+	if (!skb)
 		goto out;
-	skb = tcp_write_queue_next(sk, prev);
 
 	if (!skb_can_shift(skb) ||
-	    (skb == tcp_send_head(sk)) ||
 	    ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) ||
 	    (mss != tcp_skb_seglen(skb)))
 		goto out;
@@ -1514,7 +1514,8 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 	len = skb->len;
 	if (skb_shift(prev, skb, len)) {
 		pcount += tcp_skb_pcount(skb);
-		tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
+		tcp_shifted_skb(sk, prev, skb, state, tcp_skb_pcount(skb),
+				len, mss, 0);
 	}
 
 out:
@@ -1538,13 +1539,10 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *tmp;
 
-	tcp_for_write_queue_from(skb, sk) {
+	skb_rbtree_walk_from(skb) {
 		int in_sack = 0;
 		bool dup_sack = dup_sack_in;
 
-		if (skb == tcp_send_head(sk))
-			break;
-
 		/* queue is in-order => we can short-circuit the walk early */
 		if (!before(TCP_SKB_CB(skb)->seq, end_seq))
 			break;
@@ -1606,23 +1604,44 @@ static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk,
 	return skb;
 }
 
-/* Avoid all extra work that is being done by sacktag while walking in
- * a normal way
- */
+static struct sk_buff *tcp_sacktag_bsearch(struct sock *sk,
+					   struct tcp_sacktag_state *state,
+					   u32 seq)
+{
+	struct rb_node *parent, **p = &sk->tcp_rtx_queue.rb_node;
+	struct sk_buff *skb;
+	int unack_bytes;
+
+	while (*p) {
+		parent = *p;
+		skb = rb_to_skb(parent);
+		if (before(seq, TCP_SKB_CB(skb)->seq)) {
+			p = &parent->rb_left;
+			continue;
+		}
+		if (!before(seq, TCP_SKB_CB(skb)->end_seq)) {
+			p = &parent->rb_right;
+			continue;
+		}
+
+		state->fack_count = 0;
+		unack_bytes = TCP_SKB_CB(skb)->seq - tcp_sk(sk)->snd_una;
+		if (state->mss_now && unack_bytes > 0)
+			state->fack_count = unack_bytes / state->mss_now;
+
+		return skb;
+	}
+	return NULL;
+}
+
 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk,
 					struct tcp_sacktag_state *state,
 					u32 skip_to_seq)
 {
-	tcp_for_write_queue_from(skb, sk) {
-		if (skb == tcp_send_head(sk))
-			break;
-
-		if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq))
-			break;
+	if (skb && after(TCP_SKB_CB(skb)->seq, skip_to_seq))
+		return skb;
 
-		state->fack_count += tcp_skb_pcount(skb);
-	}
-	return skb;
+	return tcp_sacktag_bsearch(sk, state, skip_to_seq);
 }
 
 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb,
@@ -1744,8 +1763,9 @@ tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb,
 		}
 	}
 
-	skb = tcp_write_queue_head(sk);
+	state->mss_now = tcp_current_mss(sk);
 	state->fack_count = 0;
+	skb = NULL;
 	i = 0;
 
 	if (!tp->sacked_out) {
@@ -1969,7 +1989,7 @@ void tcp_enter_loss(struct sock *sk)
 	if (tcp_is_reno(tp))
 		tcp_reset_reno_sack(tp);
 
-	skb = tcp_write_queue_head(sk);
+	skb = tcp_rtx_queue_head(sk);
 	is_reneg = skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED);
 	if (is_reneg) {
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
@@ -1978,10 +1998,7 @@ void tcp_enter_loss(struct sock *sk)
 	}
 	tcp_clear_all_retrans_hints(tp);
 
-	tcp_for_write_queue(skb, sk) {
-		if (skb == tcp_send_head(sk))
-			break;
-
+	skb_rbtree_walk_from(skb) {
 		mark_lost = (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) ||
 			     is_reneg);
 		if (mark_lost)
@@ -2207,20 +2224,18 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
 	const u32 loss_high = tcp_is_sack(tp) ?  tp->snd_nxt : tp->high_seq;
 
 	WARN_ON(packets > tp->packets_out);
-	if (tp->lost_skb_hint) {
-		skb = tp->lost_skb_hint;
-		cnt = tp->lost_cnt_hint;
+	skb = tp->lost_skb_hint;
+	if (skb) {
 		/* Head already handled? */
-		if (mark_head && skb != tcp_write_queue_head(sk))
+		if (mark_head && after(TCP_SKB_CB(skb)->seq, tp->snd_una))
 			return;
+		cnt = tp->lost_cnt_hint;
 	} else {
-		skb = tcp_write_queue_head(sk);
+		skb = tcp_rtx_queue_head(sk);
 		cnt = 0;
 	}
 
-	tcp_for_write_queue_from(skb, sk) {
-		if (skb == tcp_send_head(sk))
-			break;
+	skb_rbtree_walk_from(skb) {
 		/* TODO: do this better */
 		/* this is not the most efficient way to do this... */
 		tp->lost_skb_hint = skb;
@@ -2244,7 +2259,8 @@ static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head)
 			/* If needed, chop off the prefix to mark as lost. */
 			lost = (packets - oldcnt) * mss;
 			if (lost < skb->len &&
-			    tcp_fragment(sk, skb, lost, mss, GFP_ATOMIC) < 0)
+			    tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
+					 lost, mss, GFP_ATOMIC) < 0)
 				break;
 			cnt = packets;
 		}
@@ -2328,7 +2344,7 @@ static bool tcp_any_retrans_done(const struct sock *sk)
 	if (tp->retrans_out)
 		return true;
 
-	skb = tcp_write_queue_head(sk);
+	skb = tcp_rtx_queue_head(sk);
 	if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
 		return true;
 
@@ -2369,9 +2385,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss)
 	if (unmark_loss) {
 		struct sk_buff *skb;
 
-		tcp_for_write_queue(skb, sk) {
-			if (skb == tcp_send_head(sk))
-				break;
+		skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
 			TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
 		}
 		tp->lost_out = 0;
@@ -2616,9 +2630,7 @@ void tcp_simple_retransmit(struct sock *sk)
 	unsigned int mss = tcp_current_mss(sk);
 	u32 prior_lost = tp->lost_out;
 
-	tcp_for_write_queue(skb, sk) {
-		if (skb == tcp_send_head(sk))
-			break;
+	skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
 		if (tcp_skb_seglen(skb) > mss &&
 		    !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
 			if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
@@ -2712,7 +2724,7 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
 			 * is updated in tcp_ack()). Otherwise fall back to
 			 * the conventional recovery.
 			 */
-			if (tcp_send_head(sk) &&
+			if (!tcp_write_queue_empty(sk) &&
 			    after(tcp_wnd_end(tp), tp->snd_nxt)) {
 				*rexmit = REXMIT_NEW;
 				return;
@@ -2804,9 +2816,9 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 	bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
 				    (tcp_fackets_out(tp) > tp->reordering));
 
-	if (WARN_ON(!tp->packets_out && tp->sacked_out))
+	if (!tp->packets_out && tp->sacked_out)
 		tp->sacked_out = 0;
-	if (WARN_ON(!tp->sacked_out && tp->fackets_out))
+	if (!tp->sacked_out && tp->fackets_out)
 		tp->fackets_out = 0;
 
 	/* Now state machine starts.
@@ -3076,11 +3088,11 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 prior_sacked = tp->sacked_out;
 	u32 reord = tp->packets_out;
+	struct sk_buff *skb, *next;
 	bool fully_acked = true;
 	long sack_rtt_us = -1L;
 	long seq_rtt_us = -1L;
 	long ca_rtt_us = -1L;
-	struct sk_buff *skb;
 	u32 pkts_acked = 0;
 	u32 last_in_flight = 0;
 	bool rtt_update;
@@ -3088,7 +3100,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 
 	first_ackt = 0;
 
-	while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
+	for (skb = skb_rb_first(&sk->tcp_rtx_queue); skb; skb = next) {
 		struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
 		u8 sacked = scb->sacked;
 		u32 acked_pcount;
@@ -3106,8 +3118,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 				break;
 			fully_acked = false;
 		} else {
-			/* Speedup tcp_unlink_write_queue() and next loop */
-			prefetchw(skb->next);
 			acked_pcount = tcp_skb_pcount(skb);
 		}
 
@@ -3159,12 +3169,12 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 		if (!fully_acked)
 			break;
 
-		tcp_unlink_write_queue(skb, sk);
-		sk_wmem_free_skb(sk, skb);
+		next = skb_rb_next(skb);
 		if (unlikely(skb == tp->retransmit_skb_hint))
 			tp->retransmit_skb_hint = NULL;
 		if (unlikely(skb == tp->lost_skb_hint))
 			tp->lost_skb_hint = NULL;
+		tcp_rtx_queue_unlink_and_free(skb, sk);
 	}
 
 	if (!skb)
@@ -3256,12 +3266,14 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 
 static void tcp_ack_probe(struct sock *sk)
 {
-	const struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct sk_buff *head = tcp_send_head(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 
 	/* Was it a usable window open? */
-
-	if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) {
+	if (!head)
+		return;
+	if (!after(TCP_SKB_CB(head)->end_seq, tcp_wnd_end(tp))) {
 		icsk->icsk_backoff = 0;
 		inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
 		/* Socket must be waked up by subsequent tcp_data_snd_check().
@@ -3381,7 +3393,7 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
 			tp->pred_flags = 0;
 			tcp_fast_path_check(sk);
 
-			if (tcp_send_head(sk))
+			if (!tcp_write_queue_empty(sk))
 				tcp_slow_start_after_idle_check(sk);
 
 			if (nwin > tp->max_window) {
@@ -3566,8 +3578,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	sack_state.first_sackt = 0;
 	sack_state.rate = &rs;
 
-	/* We very likely will need to access write queue head. */
-	prefetchw(sk->sk_write_queue.next);
+	/* We very likely will need to access rtx queue. */
+	prefetch(sk->tcp_rtx_queue.rb_node);
 
 	/* If the ack is older than previous acks
 	 * then we can probably ignore it.
@@ -3681,8 +3693,7 @@ no_queue:
 	 * being used to time the probes, and is probably far higher than
 	 * it needs to be for normal retransmission.
 	 */
-	if (tcp_send_head(sk))
-		tcp_ack_probe(sk);
+	tcp_ack_probe(sk);
 
 	if (tp->tlp_high_seq)
 		tcp_process_tlp_ack(sk, ack, flag);
@@ -4335,7 +4346,7 @@ static void tcp_ofo_queue(struct sock *sk)
 
 	p = rb_first(&tp->out_of_order_queue);
 	while (p) {
-		skb = rb_entry(p, struct sk_buff, rbnode);
+		skb = rb_to_skb(p);
 		if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
 			break;
 
@@ -4399,7 +4410,7 @@ static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb,
 static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct rb_node **p, *q, *parent;
+	struct rb_node **p, *parent;
 	struct sk_buff *skb1;
 	u32 seq, end_seq;
 	bool fragstolen;
@@ -4458,7 +4469,7 @@ coalesce_done:
 	parent = NULL;
 	while (*p) {
 		parent = *p;
-		skb1 = rb_entry(parent, struct sk_buff, rbnode);
+		skb1 = rb_to_skb(parent);
 		if (before(seq, TCP_SKB_CB(skb1)->seq)) {
 			p = &parent->rb_left;
 			continue;
@@ -4503,9 +4514,7 @@ insert:
 
 merge_right:
 	/* Remove other segments covered by skb. */
-	while ((q = rb_next(&skb->rbnode)) != NULL) {
-		skb1 = rb_entry(q, struct sk_buff, rbnode);
-
+	while ((skb1 = skb_rb_next(skb)) != NULL) {
 		if (!after(end_seq, TCP_SKB_CB(skb1)->seq))
 			break;
 		if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
@@ -4520,7 +4529,7 @@ merge_right:
 		tcp_drop(sk, skb1);
 	}
 	/* If there is no skb after us, we are the last_skb ! */
-	if (!q)
+	if (!skb1)
 		tp->ooo_last_skb = skb;
 
 add_sack:
@@ -4706,7 +4715,7 @@ static struct sk_buff *tcp_skb_next(struct sk_buff *skb, struct sk_buff_head *li
 	if (list)
 		return !skb_queue_is_last(list, skb) ? skb->next : NULL;
 
-	return rb_entry_safe(rb_next(&skb->rbnode), struct sk_buff, rbnode);
+	return skb_rb_next(skb);
 }
 
 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
@@ -4727,7 +4736,7 @@ static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
 }
 
 /* Insert skb into rb tree, ordered by TCP_SKB_CB(skb)->seq */
-static void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
+void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
 {
 	struct rb_node **p = &root->rb_node;
 	struct rb_node *parent = NULL;
@@ -4735,7 +4744,7 @@ static void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
 
 	while (*p) {
 		parent = *p;
-		skb1 = rb_entry(parent, struct sk_buff, rbnode);
+		skb1 = rb_to_skb(parent);
 		if (before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb1)->seq))
 			p = &parent->rb_left;
 		else
@@ -4854,26 +4863,19 @@ static void tcp_collapse_ofo_queue(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb, *head;
-	struct rb_node *p;
 	u32 start, end;
 
-	p = rb_first(&tp->out_of_order_queue);
-	skb = rb_entry_safe(p, struct sk_buff, rbnode);
+	skb = skb_rb_first(&tp->out_of_order_queue);
 new_range:
 	if (!skb) {
-		p = rb_last(&tp->out_of_order_queue);
-		/* Note: This is possible p is NULL here. We do not
-		 * use rb_entry_safe(), as ooo_last_skb is valid only
-		 * if rbtree is not empty.
-		 */
-		tp->ooo_last_skb = rb_entry(p, struct sk_buff, rbnode);
+		tp->ooo_last_skb = skb_rb_last(&tp->out_of_order_queue);
 		return;
 	}
 	start = TCP_SKB_CB(skb)->seq;
 	end = TCP_SKB_CB(skb)->end_seq;
 
 	for (head = skb;;) {
-		skb = tcp_skb_next(skb, NULL);
+		skb = skb_rb_next(skb);
 
 		/* Range is terminated when we see a gap or when
 		 * we are at the queue end.
@@ -4916,14 +4918,14 @@ static bool tcp_prune_ofo_queue(struct sock *sk)
 	do {
 		prev = rb_prev(node);
 		rb_erase(node, &tp->out_of_order_queue);
-		tcp_drop(sk, rb_entry(node, struct sk_buff, rbnode));
+		tcp_drop(sk, rb_to_skb(node));
 		sk_mem_reclaim(sk);
 		if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
 		    !tcp_under_memory_pressure(sk))
 			break;
 		node = prev;
 	} while (node);
-	tp->ooo_last_skb = rb_entry(prev, struct sk_buff, rbnode);
+	tp->ooo_last_skb = rb_to_skb(prev);
 
 	/* Reset SACK state.  A conforming SACK implementation will
 	 * do the same at a timeout based retransmit.  When a connection
@@ -5538,7 +5540,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 				    struct tcp_fastopen_cookie *cookie)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
+	struct sk_buff *data = tp->syn_data ? tcp_rtx_queue_head(sk) : NULL;
 	u16 mss = tp->rx_opt.mss_clamp, try_exp = 0;
 	bool syn_drop = false;
 
@@ -5573,9 +5575,8 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 	tcp_fastopen_cache_set(sk, mss, cookie, syn_drop, try_exp);
 
 	if (data) { /* Retransmit unacked data in SYN */
-		tcp_for_write_queue_from(data, sk) {
-			if (data == tcp_send_head(sk) ||
-			    __tcp_retransmit_skb(sk, data, 1))
+		skb_rbtree_walk_from(data) {
+			if (__tcp_retransmit_skb(sk, data, 1))
 				break;
 		}
 		tcp_rearm_rto(sk);

net/ipv4/tcp_ipv4.c

@@ -480,7 +480,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
 					       TCP_TIMEOUT_INIT;
 		icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
 
-		skb = tcp_write_queue_head(sk);
+		skb = tcp_rtx_queue_head(sk);
 		BUG_ON(!skb);
 
 		tcp_mstamp_refresh(tp);

net/ipv4/tcp_output.c

@@ -66,15 +66,17 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 			   int push_one, gfp_t gfp);
 
 /* Account for new data that has been sent to the network. */
-static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
+static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	unsigned int prior_packets = tp->packets_out;
 
-	tcp_advance_send_head(sk, skb);
 	tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
 
+	__skb_unlink(skb, &sk->sk_write_queue);
+	tcp_rbtree_insert(&sk->tcp_rtx_queue, skb);
+
 	tp->packets_out += tcp_skb_pcount(skb);
 	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
 		tcp_rearm_rto(sk);
@@ -1249,12 +1251,25 @@ static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2)
 	TCP_SKB_CB(skb)->eor = 0;
 }
 
+/* Insert buff after skb on the write or rtx queue of sk.  */
+static void tcp_insert_write_queue_after(struct sk_buff *skb,
+					 struct sk_buff *buff,
+					 struct sock *sk,
+					 enum tcp_queue tcp_queue)
+{
+	if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE)
+		__skb_queue_after(&sk->sk_write_queue, skb, buff);
+	else
+		tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
+}
+
 /* Function to create two new TCP segments.  Shrinks the given segment
  * to the specified size and appends a new segment with the rest of the
  * packet to the list.  This won't be called frequently, I hope.
  * Remember, these are still headerless SKBs at this point.
  */
-int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
+int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+		 struct sk_buff *skb, u32 len,
 		 unsigned int mss_now, gfp_t gfp)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -1337,7 +1352,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 
 	/* Link BUFF into the send queue. */
 	__skb_header_release(buff);
-	tcp_insert_write_queue_after(skb, buff, sk);
+	tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
 	list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor);
 
 	return 0;
@@ -1625,10 +1640,10 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
 		 * is caused by insufficient sender buffer:
 		 * 1) just sent some data (see tcp_write_xmit)
 		 * 2) not cwnd limited (this else condition)
-		 * 3) no more data to send (null tcp_send_head )
+		 * 3) no more data to send (tcp_write_queue_empty())
 		 * 4) application is hitting buffer limit (SOCK_NOSPACE)
 		 */
-		if (!tcp_send_head(sk) && sk->sk_socket &&
+		if (tcp_write_queue_empty(sk) && sk->sk_socket &&
 		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
 		    (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
 			tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
@@ -1824,7 +1839,8 @@ static bool tcp_snd_wnd_test(const struct tcp_sock *tp,
  * know that all the data is in scatter-gather pages, and that the
  * packet has never been sent out before (and thus is not cloned).
  */
-static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
+static int tso_fragment(struct sock *sk, enum tcp_queue tcp_queue,
+			struct sk_buff *skb, unsigned int len,
 			unsigned int mss_now, gfp_t gfp)
 {
 	struct sk_buff *buff;
@@ -1833,7 +1849,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 
 	/* All of a TSO frame must be composed of paged data.  */
 	if (skb->len != skb->data_len)
-		return tcp_fragment(sk, skb, len, mss_now, gfp);
+		return tcp_fragment(sk, tcp_queue, skb, len, mss_now, gfp);
 
 	buff = sk_stream_alloc_skb(sk, 0, gfp, true);
 	if (unlikely(!buff))
@@ -1869,7 +1885,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 
 	/* Link BUFF into the send queue. */
 	__skb_header_release(buff);
-	tcp_insert_write_queue_after(skb, buff, sk);
+	tcp_insert_write_queue_after(skb, buff, sk, tcp_queue);
 
 	return 0;
 }
@@ -1939,8 +1955,10 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb,
 			goto send_now;
 	}
 
-	head = tcp_write_queue_head(sk);
-
+	/* TODO : use tsorted_sent_queue ? */
+	head = tcp_rtx_queue_head(sk);
+	if (!head)
+		goto send_now;
 	age = tcp_stamp_us_delta(tp->tcp_mstamp, head->skb_mstamp);
 	/* If next ACK is likely to come too late (half srtt), do not defer */
 	if (age < (tp->srtt_us >> 4))
@@ -2158,13 +2176,12 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
 	limit <<= factor;
 
 	if (refcount_read(&sk->sk_wmem_alloc) > limit) {
-		/* Always send the 1st or 2nd skb in write queue.
+		/* Always send skb if rtx queue is empty.
 		 * No need to wait for TX completion to call us back,
 		 * after softirq/tasklet schedule.
 		 * This helps when TX completions are delayed too much.
 		 */
-		if (skb == sk->sk_write_queue.next ||
-		    skb->prev == sk->sk_write_queue.next)
+		if (tcp_rtx_queue_empty(sk))
 			return false;
 
 		set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
@@ -2215,7 +2232,7 @@ void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
 	 * it's the "most interesting" or current chrono we are
 	 * tracking and starts busy chrono if we have pending data.
 	 */
-	if (tcp_write_queue_empty(sk))
+	if (tcp_rtx_and_write_queues_empty(sk))
 		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
 	else if (type == tp->chrono_type)
 		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
@@ -2310,7 +2327,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 						    nonagle);
 
 		if (skb->len > limit &&
-		    unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
+		    unlikely(tso_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
+					  skb, limit, mss_now, gfp)))
 			break;
 
 		if (test_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags))
@@ -2350,7 +2368,7 @@ repair:
 		tcp_cwnd_validate(sk, is_cwnd_limited);
 		return false;
 	}
-	return !tp->packets_out && tcp_send_head(sk);
+	return !tp->packets_out && !tcp_write_queue_empty(sk);
 }
 
 bool tcp_schedule_loss_probe(struct sock *sk)
@@ -2374,7 +2392,7 @@ bool tcp_schedule_loss_probe(struct sock *sk)
 		return false;
 
 	if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
-	     tcp_send_head(sk))
+	     !tcp_write_queue_empty(sk))
 		return false;
 
 	/* Probe timeout is 2*rtt. Add minimum RTO to account
@@ -2427,18 +2445,14 @@ void tcp_send_loss_probe(struct sock *sk)
 	int mss = tcp_current_mss(sk);
 
 	skb = tcp_send_head(sk);
-	if (skb) {
-		if (tcp_snd_wnd_test(tp, skb, mss)) {
-			pcount = tp->packets_out;
-			tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
-			if (tp->packets_out > pcount)
-				goto probe_sent;
-			goto rearm_timer;
-		}
-		skb = tcp_write_queue_prev(sk, skb);
-	} else {
-		skb = tcp_write_queue_tail(sk);
+	if (skb && tcp_snd_wnd_test(tp, skb, mss)) {
+		pcount = tp->packets_out;
+		tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
+		if (tp->packets_out > pcount)
+			goto probe_sent;
+		goto rearm_timer;
 	}
+	skb = skb_rb_last(&sk->tcp_rtx_queue);
 
 	/* At most one outstanding TLP retransmission. */
 	if (tp->tlp_high_seq)
@@ -2456,10 +2470,11 @@ void tcp_send_loss_probe(struct sock *sk)
 		goto rearm_timer;
 
 	if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
-		if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss,
+		if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb,
+					  (pcount - 1) * mss, mss,
 					  GFP_ATOMIC)))
 			goto rearm_timer;
-		skb = tcp_write_queue_next(sk, skb);
+		skb = skb_rb_next(skb);
 	}
 
 	if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
@@ -2659,7 +2674,7 @@ void tcp_skb_collapse_tstamp(struct sk_buff *skb,
 static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
+	struct sk_buff *next_skb = skb_rb_next(skb);
 	int skb_size, next_skb_size;
 
 	skb_size = skb->len;
@@ -2676,8 +2691,6 @@ static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 	}
 	tcp_highest_sack_combine(sk, next_skb, skb);
 
-	tcp_unlink_write_queue(next_skb, sk);
-
 	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
 		skb->ip_summed = CHECKSUM_PARTIAL;
 
@@ -2705,7 +2718,7 @@ static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 
 	tcp_skb_collapse_tstamp(skb, next_skb);
 
-	sk_wmem_free_skb(sk, next_skb);
+	tcp_rtx_queue_unlink_and_free(next_skb, sk);
 	return true;
 }
 
@@ -2716,8 +2729,6 @@ static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
 		return false;
 	if (skb_cloned(skb))
 		return false;
-	if (skb == tcp_send_head(sk))
-		return false;
 	/* Some heuristics for collapsing over SACK'd could be invented */
 	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
 		return false;
@@ -2740,7 +2751,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
 	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
 		return;
 
-	tcp_for_write_queue_from_safe(skb, tmp, sk) {
+	skb_rbtree_walk_from_safe(skb, tmp) {
 		if (!tcp_can_collapse(sk, skb))
 			break;
 
@@ -2815,7 +2826,8 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 
 	len = cur_mss * segs;
 	if (skb->len > len) {
-		if (tcp_fragment(sk, skb, len, cur_mss, GFP_ATOMIC))
+		if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len,
+				 cur_mss, GFP_ATOMIC))
 			return -ENOMEM; /* We'll try again later. */
 	} else {
 		if (skb_unclone(skb, GFP_ATOMIC))
@@ -2906,29 +2918,24 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 void tcp_xmit_retransmit_queue(struct sock *sk)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
+	struct sk_buff *skb, *rtx_head = NULL, *hole = NULL;
 	struct tcp_sock *tp = tcp_sk(sk);
-	struct sk_buff *skb;
-	struct sk_buff *hole = NULL;
 	u32 max_segs;
 	int mib_idx;
 
 	if (!tp->packets_out)
 		return;
 
-	if (tp->retransmit_skb_hint) {
-		skb = tp->retransmit_skb_hint;
-	} else {
-		skb = tcp_write_queue_head(sk);
+	skb = tp->retransmit_skb_hint;
+	if (!skb) {
+		rtx_head = tcp_rtx_queue_head(sk);
+		skb = rtx_head;
 	}
-
 	max_segs = tcp_tso_segs(sk, tcp_current_mss(sk));
-	tcp_for_write_queue_from(skb, sk) {
+	skb_rbtree_walk_from(skb) {
 		__u8 sacked;
 		int segs;
 
-		if (skb == tcp_send_head(sk))
-			break;
-
 		if (tcp_pacing_check(sk))
 			break;
 
@@ -2973,7 +2980,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 		if (tcp_in_cwnd_reduction(sk))
 			tp->prr_out += tcp_skb_pcount(skb);
 
-		if (skb == tcp_write_queue_head(sk) &&
+		if (skb == rtx_head &&
 		    icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT)
 			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 						  inet_csk(sk)->icsk_rto,
@@ -3015,12 +3022,15 @@ void tcp_send_fin(struct sock *sk)
 	 * Note: in the latter case, FIN packet will be sent after a timeout,
 	 * as TCP stack thinks it has already been transmitted.
 	 */
-	if (tskb && (tcp_send_head(sk) || tcp_under_memory_pressure(sk))) {
+	if (!tskb && tcp_under_memory_pressure(sk))
+		tskb = skb_rb_last(&sk->tcp_rtx_queue);
+
+	if (tskb) {
 coalesce:
 		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
 		TCP_SKB_CB(tskb)->end_seq++;
 		tp->write_seq++;
-		if (!tcp_send_head(sk)) {
+		if (tcp_write_queue_empty(sk)) {
 			/* This means tskb was already sent.
 			 * Pretend we included the FIN on previous transmit.
 			 * We need to set tp->snd_nxt to the value it would have
@@ -3086,9 +3096,9 @@ int tcp_send_synack(struct sock *sk)
 {
 	struct sk_buff *skb;
 
-	skb = tcp_write_queue_head(sk);
+	skb = tcp_rtx_queue_head(sk);
 	if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) {
-		pr_debug("%s: wrong queue state\n", __func__);
+		pr_err("%s: wrong queue state\n", __func__);
 		return -EFAULT;
 	}
 	if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) {
@@ -3101,10 +3111,9 @@ int tcp_send_synack(struct sock *sk)
 			if (!nskb)
 				return -ENOMEM;
 			INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor);
-			tcp_unlink_write_queue(skb, sk);
+			tcp_rtx_queue_unlink_and_free(skb, sk);
 			__skb_header_release(nskb);
-			__tcp_add_write_queue_head(sk, nskb);
-			sk_wmem_free_skb(sk, skb);
+			tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb);
 			sk->sk_wmem_queued += nskb->truesize;
 			sk_mem_charge(sk, nskb->truesize);
 			skb = nskb;
@@ -3327,7 +3336,6 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
 
 	tcb->end_seq += skb->len;
 	__skb_header_release(skb);
-	__tcp_add_write_queue_tail(sk, skb);
 	sk->sk_wmem_queued += skb->truesize;
 	sk_mem_charge(sk, skb->truesize);
 	tp->write_seq = tcb->end_seq;
@@ -3405,12 +3413,13 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 	TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;
 	if (!err) {
 		tp->syn_data = (fo->copied > 0);
+		tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data);
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);
 		goto done;
 	}
 
-	/* data was not sent, this is our new send_head */
-	sk->sk_send_head = syn_data;
+	/* data was not sent, put it in write_queue */
+	__skb_queue_tail(&sk->sk_write_queue, syn_data);
 	tp->packets_out -= tcp_skb_pcount(syn_data);
 
 fallback:
@@ -3453,6 +3462,7 @@ int tcp_connect(struct sock *sk)
 	tp->retrans_stamp = tcp_time_stamp(tp);
 	tcp_connect_queue_skb(sk, buff);
 	tcp_ecn_send_syn(sk, buff);
+	tcp_rbtree_insert(&sk->tcp_rtx_queue, buff);
 
 	/* Send off SYN; include data in Fast Open. */
 	err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
@@ -3647,7 +3657,8 @@ int tcp_write_wakeup(struct sock *sk, int mib)
 		    skb->len > mss) {
 			seg_size = min(seg_size, mss);
 			TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
-			if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC))
+			if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE,
+					 skb, seg_size, mss, GFP_ATOMIC))
 				return -1;
 		} else if (!tcp_skb_pcount(skb))
 			tcp_set_skb_tso_segs(skb, mss);
@@ -3677,7 +3688,7 @@ void tcp_send_probe0(struct sock *sk)
 
 	err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE);
 
-	if (tp->packets_out || !tcp_send_head(sk)) {
+	if (tp->packets_out || tcp_write_queue_empty(sk)) {
 		/* Cancel probe timer, if it is not required. */
 		icsk->icsk_probes_out = 0;
 		icsk->icsk_backoff = 0;

net/ipv4/tcp_timer.c

@@ -156,8 +156,13 @@ static bool retransmits_timed_out(struct sock *sk,
 		return false;
 
 	start_ts = tcp_sk(sk)->retrans_stamp;
-	if (unlikely(!start_ts))
-		start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk));
+	if (unlikely(!start_ts)) {
+		struct sk_buff *head = tcp_rtx_queue_head(sk);
+
+		if (!head)
+			return false;
+		start_ts = tcp_skb_timestamp(head);
+	}
 
 	if (likely(timeout == 0)) {
 		linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base);
@@ -304,11 +309,12 @@ static void tcp_delack_timer(unsigned long data)
 static void tcp_probe_timer(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct sk_buff *skb = tcp_send_head(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	int max_probes;
 	u32 start_ts;
 
-	if (tp->packets_out || !tcp_send_head(sk)) {
+	if (tp->packets_out || !skb) {
 		icsk->icsk_probes_out = 0;
 		return;
 	}
@@ -321,9 +327,9 @@ static void tcp_probe_timer(struct sock *sk)
 	 * corresponding system limit. We also implement similar policy when
 	 * we use RTO to probe window in tcp_retransmit_timer().
 	 */
-	start_ts = tcp_skb_timestamp(tcp_send_head(sk));
+	start_ts = tcp_skb_timestamp(skb);
 	if (!start_ts)
-		tcp_send_head(sk)->skb_mstamp = tp->tcp_mstamp;
+		skb->skb_mstamp = tp->tcp_mstamp;
 	else if (icsk->icsk_user_timeout &&
 		 (s32)(tcp_time_stamp(tp) - start_ts) >
 		 jiffies_to_msecs(icsk->icsk_user_timeout))
@@ -408,7 +414,7 @@ void tcp_retransmit_timer(struct sock *sk)
 	if (!tp->packets_out)
 		goto out;
 
-	WARN_ON(tcp_write_queue_empty(sk));
+	WARN_ON(tcp_rtx_queue_empty(sk));
 
 	tp->tlp_high_seq = 0;
 
@@ -441,7 +447,7 @@ void tcp_retransmit_timer(struct sock *sk)
 			goto out;
 		}
 		tcp_enter_loss(sk);
-		tcp_retransmit_skb(sk, tcp_write_queue_head(sk), 1);
+		tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1);
 		__sk_dst_reset(sk);
 		goto out_reset_timer;
 	}
@@ -473,7 +479,7 @@ void tcp_retransmit_timer(struct sock *sk)
 
 	tcp_enter_loss(sk);
 
-	if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk), 1) > 0) {
+	if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) {
 		/* Retransmission failed because of local congestion,
 		 * do not backoff.
 		 */
@@ -647,7 +653,7 @@ static void tcp_keepalive_timer (unsigned long data)
 	elapsed = keepalive_time_when(tp);
 
 	/* It is alive without keepalive 8) */
-	if (tp->packets_out || tcp_send_head(sk))
+	if (tp->packets_out || !tcp_write_queue_empty(sk))
 		goto resched;
 
 	elapsed = keepalive_time_elapsed(tp);

net/sched/sch_netem.c

@@ -148,12 +148,6 @@ struct netem_skb_cb {
 	psched_time_t	time_to_send;
 };
 
-
-static struct sk_buff *netem_rb_to_skb(struct rb_node *rb)
-{
-	return rb_entry(rb, struct sk_buff, rbnode);
-}
-
 static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
 {
 	/* we assume we can use skb next/prev/tstamp as storage for rb_node */
@@ -364,7 +358,7 @@ static void tfifo_reset(struct Qdisc *sch)
 	struct rb_node *p = rb_first(&q->t_root);
 
 	while (p) {
-		struct sk_buff *skb = netem_rb_to_skb(p);
+		struct sk_buff *skb = rb_to_skb(p);
 
 		p = rb_next(p);
 		rb_erase(&skb->rbnode, &q->t_root);
@@ -382,7 +376,7 @@ static void tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
 		struct sk_buff *skb;
 
 		parent = *p;
-		skb = netem_rb_to_skb(parent);
+		skb = rb_to_skb(parent);
 		if (tnext >= netem_skb_cb(skb)->time_to_send)
 			p = &parent->rb_right;
 		else
@@ -538,7 +532,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 				struct sk_buff *t_skb;
 				struct netem_skb_cb *t_last;
 
-				t_skb = netem_rb_to_skb(rb_last(&q->t_root));
+				t_skb = skb_rb_last(&q->t_root);
 				t_last = netem_skb_cb(t_skb);
 				if (!last ||
 				    t_last->time_to_send > last->time_to_send) {
@@ -617,7 +611,7 @@ deliver:
 	if (p) {
 		psched_time_t time_to_send;
 
-		skb = netem_rb_to_skb(p);
+		skb = rb_to_skb(p);
 
 		/* if more time remaining? */
 		time_to_send = netem_skb_cb(skb)->time_to_send;